We propose to continue our work on the activation reaction of pyruvate oxidase which leads to a new form of the enzyme which is 20-300 fold more active in catalyzing the oxidative decarboxylation of pyruvate. Activation can be accomplished either through the binding of lipids to the protein or through limited proteolysis of the native enzyme. We propose to characterize the rate-limiting steps under different assay conditions in the overall reaction and locate the reaction step which is enhanced by activation in both cases. We also propose to continue our work on the isolation and characterization of intermediates in the enzymatic halogenation reaction catalyzed by chloroperoxidase. BIBLIOGRAPHIC REFERENCES: Krejcarek, G.E., Bryant, R.G., Smith, R.J., and Hager, L.P. Broadline nuclear magnetic resonance studies of of chloroperoxidase. Biochemistry 15, 2508-2511 (1976). Chiang, R.L., Rand-Meir, T., Makino, R. and Hager, L.P. Compound X: An intermediate in enzymatic chlorination. J. Biol. Chem. 251, 6340 (1976).